Unable to see HDRI in background
In your screenshot, your view is set to Ortographic not Perspective, this usually makes the HDRI just a blurred color instead of a real image. You can toggle between those views with Numpad 5. However, then there is still color, but your viewport shows this grey checker texture which means you've set the background to Transparent. Go to Render Properties &gt; Film &gt; Transparent and disable it.